Halogen regenerative-cycle incandescent lamp

ABSTRACT

The quality and useful life of regenerative-cycle type incandescent lamps are enhanced by dosing the lamp with a carefully controlled amount of carbon tetrabromide that is vaporized and admixed with an inert fill gas, such as a mixture of 90 percent argon and 10 percent nitrogen. Both oxygen and hydrogen are purged from the lamp prior to the gas-filling operation and are excluded from the CBr4-dosed fill gas. A method for filling such lamps with a mixture of an inert gas and a small carefully-controlled amount of vaporized halogen-containing material that is monitored by infrared measuring techniques is also disclosed.

United States Patent Yannopoulos et al.

[151 3,707,643 1 51 Dec. 26, 1972 [54] HALOGEN REGENERATIVE-CYCLEINCANDESCENT LAMP [72] Inventors: Lymperios N. Yannopoulos; Alfred H.Pebler, both of Pittsburgh, Pa.

, [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa. 22 Filed: June30, 1971 211 Appl.No.: 158,435

[52] US. Cl 313/222, 313/226 [51] Int. Cl. ..H01k 7/00 [58] Field ofSearch ..313/222 [56] References Cited 'UNlTED STATES PATENTS 5/1963Shurgan 313 222 Sugano et a1. ..3l3/222 Primary Examiner-Roy LakeAssistant Examiner-Darwin R. l-lostetter Attorney-A. T. Stratton et a1.

['57] ABSTRACT The quality and useful life of regenerative-cycle typeincandescent lamps are enhanced by dosing the lamp with a carefullycontrolled amount of carbon tetrabromide that is vaporized and admixedwith an inert fill gas, such as a mixture of 90 percent argon and 10percent nitrogen. Both oxygen and hydrogen are purged from the lampprior to the gas-filling operation and are excluded from the CBr -d0sedfill gas. A method for filling such lamps with a mixture of an inertgasand a small carefully-controlled amount of vaporized halogen-containingmaterial that is monitored by infrared measuring techniques is alsodisclosed.

I Y 4 Claims, 2 Drawing Figures PATENTED I97? 3. 707,643

RESERVOIR 32 |NERT INERT FIL L FLUSH --@--0 HYDROGEN GAS GAS 3| 0 36 34I 33 H62 VAC UUM WITNESSES QNVENTORS M Lympenos N.Yonnopoulos QM MbL.Aifred R. Pebler AGENT HALOGEN REGENERATIVE-CYCLE INCANDESCENT LAMPFIELD OF THE INVENTION This invention relates to electric incandescentlamps and has particular reference to a regenerative-cycle type of lampthat contains a tungsten filament and a halogen atmosphere.

DESCRIPTION OF THE PRIOR ART Halogen incandescent lamps are well knownin the art and a lamp of this type in which the regenerative cycleissustained by an inert fill gas that contains a small quantity ofiodine is described in U.S. Pat. No. 2,883,571 to E.G. Fridrich et al.Lamps of this type in which bromine is used as the halogen incombination with hydrogen are also well known in the art and aredisclosed in U.S. Pat. No. 3,538,373 issued to P.C. van der Linden etal. The concept of dosing such lamps with small amounts of both bromineand iodine, either alone or in combination with hydrogen, is disclosedin U.S. Pat. No. 3,453,476 and the use of carbon tetrabromide per se indosing lamps of this type is disclosed in U.S. Pat. Nos. 3,431,448 and3,510,189.

Despite the many recent improvements made in halogen incandescent lampsexperience has shown that when bromine is employed as the halogenadditive premature blackening of the lamp envelope and a correspondingreduction in the useful life of the lamp sometimes occurs. This isparticularly true of lamps that have been dosed with methylene bromide(CH Br and thus have an atmosphere that contains both hydrogen andbromine. In addition, CH Br is toxic and requires safeguards whichcomplicates the manufacture of such lamps under factory conditions.

SUMMARY OF THE INVENTION The foregoing quality and manufacturingproblems are solved in accordance with the present invention bydosingsuch regenerative-type lamps with carefully controlled amounts ofcarbon tetrabromide (CBr,,) to provide small but critical quantities ofbromine within the operating lamps, and by excluding both hydrogen andoxygen from the lamp atmosphere. Lamps made in accordance with theinvention burn beyond their design life of 2000 hours without exhibitingenvelopeblackening or destructive etching of the tungsten filamentorinner leads. The non-corrosive nature and relative nontoxicity of CBr,greatly facilitates lamp manufacture under factory conditions andpermits the halogen additive to be admixed with the inert fill gaswithout contaminating the lamp with hydrogen or oxygen.

The amount of bromine and carbon introduced into the lamp is carefullycontrolled by measuring the quantity of CBr vapor present in the inertfill gas prior to its *introduction into the lamp. This is achieved bymaking the gas-sampling component of an infrared analyzing instrument anintegral part of the gas-filling system and comparing the amount ofinfrared energy absorbed by the halogen-dosed fill gas with thatabsorbed by a gas of known composition in the reference cell componentof the analyzer. This permits thus also provides a unique and practicalmethod of dosing a regenerative-cycle type incandescent lamps to bedosed with a preciselycontrolled amount of CBI4 which dissociates withinthe operating lamp and provides a small but critical amount of elementalbromine that insures that the lamp will operate without prematureblackening.

Both hydrogen and oxygen are excluded from the lamp atmosphere bysubjecting the lamp to a series of flushing cycles and afilament-flashing operation prior to filling it with the CBr -dosedinert gas.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the inventionwill be obtained from the exemplary embodiment of the invention shown inthe accompanying drawing, wherein:

FIG. 1 is an enlarged side elevational view of a representative halogenregenerative-cycle incandescent lamp that incorporates the invention;and

FIG. 2 is a schematic of a preferred system for closing an inert fillgas with measured amounts of CBr purging the lamp of impurities andevacuating it, and then introducing the CBr -dosed fill gas into thelamp.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a 400watt T4 halogen incandescent lamp 10 which is representative of the typeof lamp to which the present invention is addressed. The lamp I0 isdesigned to operate on a volt power source for 2000 hours. It has atubular envelope 12 of suitable light-transmitting material, such asquartz, that has a high melting point and can thus withstand theelevated operating temperatures involved without' becoming deformed.

The envelope 12 is hermetically sealed by a protruding tipped-offsegment 13 of an exhaust tubulation and by press seals 14 formed at eachof its ends. A coiledcoil tungsten filament I6 is longitudinallysuspended within the envelope I2 and is held in such position by a pairof tungsten inner leads 18 that are secured to the ends of the filamentcoil 16 and have their opposite ends embedded in the respective pressseals 14. The embedded ends of the tungsten leads 18 are electricallyconnected to strips 19 of molybdenum foil that are also embedded in therespective seals 14 and, in turn, are fastened to outer leads 20 ofmolybdenum that are terminated by metal contactor buttons 21 which serveas the lamp terminals. The protruding ends of the lead-in conductor andterminal assemblies are protectively enclosed in ceramic sleeves 22 thatare secured to the respective press seals I4 within a suitable cement inaccordance with standard lamp-making practice.

The physical size of the coiled-coil filament l6 relative to that of thetubular envelope 12 is such that the bulb wall operates at a temperatureof at least 250C, and preferably at 500 to 700C, when the lamp 10 isoperated at its rated voltage and wattage.

In accordance with the present invention the envelope 12 contains asmall but critical amount of carbon tetrabromide (CBr that is in agaseous or vaporous state and admixed with a suitable inert fill gassuch as nitrogen, argon, krypton or xenon and mixtures thereof. Theamount of CBL, introduced into the lamp 10 is carefully controlled sothat from about 0.015 to 0.075 micromole of bromine per cc. of envelopevolume is provided when the lamp 10 is energized and the CBr isthermally decomposed.

' from about 0.02 to 0.09'percent CBr Specific examples of thecalculated partial pressure, micromoles of CBr, and elemental bromineper cc. of envelope volume, and the partial pressure of elementalbromine for various measuredtconcentrations of CBr, dosed into the 90percent argon-1O percent nitrogen fill gas within the aforementionedrange are given below in Table l.

TABLEl Amt. of Partial Micromole Micromole Partial CBr. in Pressure ofCBr. of Br, Pressure Fill Gas 1 of CBr, (per cc (per cc of Br (torr) ofVolume) of Volume) (torr) An important feature of the invention is thepurging of both oxygen and hydrogen from the lamp envelope 12 andfilament 16 during lamp manufacture, and the exclusion of both of theseelements from the CBr dosed fill gas introduced into the lamp 10. Bycarefully controlling the purity of the halogen additive and fill gasconstituents and purging the lamp of impurities prior to the gas-fillingoperation (as described below), the hydrogen and oxygen partial pressurehave each been maintained below 10- torr. The atmosphere of the finishedlamp 10 is, accordingly, substantially devoid of both oxygen andhydrogen.

GAS-FILLING SYSTEM In FIG. 2 there is shown a schematicrepresentation ofa preferred apparatus for dosing regenerative-cycle type lamps withcarefully controlled amounts of a terconnecting conduit-valvecombination52-53 and the other end of thecharnber 44 to a conduit 48 and a tank 50of compressed inert fill gas, such as a mixture of 90 percent argon and10 percent nitrogen.

The remaining arms of T-connectors 37 and 40 are connected to anelongated chamber 51 by a pair of in- 54-55, respectively. The chamber51 comprises the sample cell of an infrared analyzing device 56 whichpermits the CBn-content of the fill gas to be measured just before thelatter is introduced into the lamp 10. The end walls ofthe chamber 51are thus made of infrared-radiation transmitting material and, inconjunction with a similar but independent reference cell 57 and adetector-58, provides an on-line system for monitoring and controllingthe composition of the dosed fill gas. 1

supply by conduitvalve combinations 31-32, 33-34 and 35-36,respectively.

The other side of T-connector 28 is joined by a conduit to anotherT-connector 37 which, in turn, is joined by a conduit-valve combination38-39 to a third T-type connector 40. The opposite arm of T-connector 40is joined by a conduit-valve combination 42-43 to atemperature-controlled chamber 44 that contains a reservoir of CBr, insolid form and is filled with suitable means, such as loosely-packedglass granules 45, that provide a tortuous flow path through thechamber. Another conduit-valve combination 46-47 connects Infraredanalyzing instruments for accurately 'measuring the concentration of achemical compound (such as CBr in a gas are well known and utilizeinfrared sources of energy, an optical chopper, sample and referencecells, a detector and a signal recorder to measure the amount ofinfrared energy absorbed by the gas mixture in the sample cell andcompare it to the energy absorbed by a known gas in the reference cell.Infrared analyzers of this type are described in detail in Bulletin4055-D entitled BECKMAN INFRARED ANALYZERS" available from BeckmanInstruments lnc., Process Instruments Division,- Fullerton, California92634. However, such instruments have not been used in manufacturinghalogen type lamps.

' LAMP PURGING AND GAS-FILLING METHOD The sequence of steps in purgingthe lamp 10 of impurities and filling it with a carefully controlledamount of CBr -dosed fill gas using the system illustrated in FIG. 2will now be described.

Before the lamp 10 is inserted into the coupling member 24, the systemis primed by properly adjusting the temperature of the CBr, reservoirandthe velocity of the fill gas as it flows through chamber 44 from thetank 50 so that CBr vapor is entrained in the stream of fill gas at apredetermined rate. This is achieved by closing valves 32, 34, 36 and39, and opening valves 27, 53, 55, 43 and 47 so that fill gas flows fromtank 50 through the CBr reservoir 44 and sample cell 51 of the infraredanalyzer 56 and out through the open coupling member 24. When the properamount of CBr, vapor is entrained in the fill gas (as indicated by thereading obtained on infrared analyzer 56), valves'27 and 53 are closedand the system is ready for use. Valve 55 is also closed and apredetermined volume of dosed fill gas is thus trapped at a knownpressure in the enclosure defined by the sample cell 51 and associatedsegments of conduits 52, 54.

The exhaust tubulation 13 of the lamp 10 is then inserted into thecoupling member 24 and the latter is compressively locked to provide aseal. Valves 27 and 32 are then opened and the lamp 10 is thus connectedto the inert flush gas supply, preferably the argonnitrogen mixture withwhich the lamp will ultimately be filled. After the lamp 10 has beenfilled with flush gas to a suitable pressure (1 atmosphere for example),valve 32 is closed and valve 34 is opened, thus connecting the lamp 10to the vacuum system. The lamp is then exhausted to a suitable pressure,such as 1 micron of mercury for example. This completes one flush cycle.

The aforesaid sequence of operations is repeated until at least fourflush cycles have been completed and the lamp l0 and its connectingmanifold 26 have been thoroughly purged of hydrogen and oxygen and othergaseous impurities.

Prior to the gas-filling operation, and preferably between the secondand third flush cycles, the lamp filament 16 is also purged ofimpurities by opening valve 36 and connecting the evacuated lamp to thehydrogen supply (valve 32 and 34 being closed) so that the lamp isfilled with about one atmosphere of hydrogen. The filament. 16 is thenflashed by momentarily energizing it, and the lamp 10 is evacuated byclosing valve 36 and opening valve 34 in the vacuum line 33. Valve 34 iskept open until the lamp is evacuated to a pressure of about 1 micron ofmercury. The flushing operation is then resumed.

After the last flush cycle has been completed and the lamp 10 has beenevacuated to about 1 micron pressure, valve 34 is closed and valve 53 isopenedthus permitting the CBr -dosed fill gas in cell 51 and lines 52,54 to expand into the lamp envelope through the exhaust tubulation 13'and interconnecting portion of the system. The aforesaid interconnectingportion of the system consists of the portions of conduits which extendfrom coupling member 24 through connector 28 and 37 to valve 39, fromconnector 37 to valve 53, and from connector 28 to valves 32, 34 and 36through conduit 29, the 4-way connector 30 and the interposed segmentsof conduits 31, 33 and 35. The volume of this interconnecting portion ofthe system is known and calibrated. Thus, the concentration or amount ofCBr introduced into the lamp 10 can readily and accurately be controlledby correlating the dosage contained in the expanded volume of admixedCBr, and fill gas with the measurement data obtained from the gasmonitor 56.

After the lamp 10 has been charged with CBr -dosed fill gas to theproper pressure, valve 27 is closed and exhaust tubulation 13' is heatedand tipped offthus separating the lamp 10 from the system and completingthe gas-filling operation. Valve 53 is then closed, the

remnant of the tubulation 13' in coupling member 24 is removed, a newlamp 10 is connected to the system, and the above sequence of operationsis repeated.

As will be apparent to those skilled in the art, the above-describedsystem can be used to process and fill any desired number of lamps byproviding multiple coupling members and appropriately adjusting thepressure of the CBr -dosed fill gas in the calibrated volume defined bythe enclosure (that is chamber 51, etc.).-

We claim as our invention:

1. A regenerative-cycle type electric incandescent lamp comprising, incombination;

an envelope of light-transmitting material that has a high softeningpoint,

a tungsten filament sealed within said envelope and connected to a pairof spaced lead-in conductors that extend through the envelope, andhalogen-containing atmosphere within said envelope that is substantiallydevoid of oxygen and hydrogen and consists essentially of a mixture of(a) carbon tetrabromide in an amount sufficient to provide from about0.015 to 0.075 micromole of bromine per cc. of envelope volume, and (b)an inert fill gas selected from he group consisting of nitrogen, argon,krypton or xenon and mixtures thereof.

2. The lamp of claim 1 wherein the total pressure of said mixture ofcarbon tetrabromide and inert gas is within a range of from about 500 to2000 torr at room temperature.

3. The lamp of claim 1 wherein said halogen-contain ing atmosphereconsists essentially of a mixture of percent argon-l0 percent nitrogenthat initially contains from about 0.02 percent to 0.09 percent carbontetrabromide.

4. The lamp of claim 3 wherein said mixture of argon, nitrogen andcarbon tetrabromide contains less than 10" torr of oxygen, less than 10'torr of hydrogen, and is at a total pressure of from about 600 to 1000torr.

2. The lamp of claim 1 wherein the total pressure of said mixture ofcarbon tetrabromide and inert gas is within a range of from about 500 to2000 torr at room temperature.
 3. The lamp of claim 1 wherein saidhalogen-containing atmosphere consists essentially of a mixture of 90percent argon-10 percent nitrogen that initially contains from about0.02 percent to 0.09 percent carbon tetrabromide.
 4. The lamp of claim 3wherein said mixture of argon, nitrogen and carbon tetrabromide containsless than 10 2 torr of oxygen, less than 10 2 torr of hydrogen, and isat a total pressure of from about 600 to 1000 torr.